As the demands for multi-functional integrated circuits increase, more and more levels of metal interconnects are required to satisfy such increase in device complexity. Tungsten has become the metal interconnect of choice because of its low contact resistance and its ability to be deposited onto the semiconductor substrate by a variety of methods, such as sputtering, physical vapor deposition, and chemical vapor deposition. Chemical vapor deposition is a process in which chemical reactions between gaseous molecules react within a chamber thereby resulting in the formation of thin metallic films, and has been particularly favored for the formation of tungsten contacts because of its excellent gap-filling property. Such gap-filling property, or the ability to provide complete step coverage of the feature size, becomes even more critical as semiconductor devices challenge the sub-micron regime with ever-shrinking feature sizes.
U.S. Pat. Nos. 6,635,965, 6,593,233, 6,271,129, and 5,371,041 disclose conventional techniques for forming tungsten contacts within the layers of semiconductor wafers by chemical vapor deposition. Unfortunately, such conventional techniques typically result in the formation of voids within the metal contacts, which can detrimentally affect the overall performance of the contacts. In many cases, these conventional techniques have been resulted in voids in upwards of about 25 nm to 30 nm, which can seriously affect overall device performance. Accordingly, what is needed is a technique for forming metal contacts within semiconductor layers that does not suffer from the deficiencies of conventional techniques.